What does the subject Demonology entale?

My name is Jess and I am about to be a junior in high school. I was recently told about a subject called Demonology but I know little to nothing about it. It seems to me that it is similar to that paranormal activity bs, and in that case interests me little; but I could be dead wrong. The fact is that I am a devout non-denominational Christian and I do not believe in ghosts, but I do believe in demonic possession and inhabitaion of certain places. I'm currently at a loss as to what area of study I should go into after high school, so I'm basically just exhausting all of my options. Any and all help would be much appreciated. Thank you.